1. Field of the Invention
The present invention relates to a print head, and more particularly, to a driving circuit and control method for a print head installed in an inkjet printer.
2. Description of the Related Art
FIG. 1 shows a conventional print head 10. A plurality of nozzles 11 are arranged in a matrix on a board 12 for dispersing drops of ink on a print surface. A driving circuit (not shown) is installed on a board 12 for controlling corresponding nozzles 11. The driving circuit is coupled to corresponding I/O pins through a flexible cable installed on a flexible printed circuit board 14. Referring to FIG. 2, a control signal output from a controller 20 based on image data from a printer 2 is applied to the print head 10 through I/O pads 16 to the driving circuit for driving the nozzles 11 to disperse drops of ink.
The driving circuit is shown in FIG. 3. The driving circuit 18 has a plurality of address lines A1˜AN, and bank lines B1˜BN arranged in an array, each enable circuit 180 is controlled by a corresponding address line A1˜AN and a bank line B1˜BN for controlling a corresponding heating element R1˜RK. Each of the enable circuits 180 has a transistor N1˜NK serving as a switch for activating a corresponding heating element R1˜RK. When the heating element R1˜RK is activated, ink is dispersed through corresponding nozzles (not shown).
According to the described method, the number of nozzles of a print head is equal to the number of address lines multiplied by the number of bank lines. For example, if there are 20 address lines and 20 bank lines disposed in a printer, 400 nozzles are controlled by the address lines and the bank lines (20×20=400). When the number of nozzles increases, the number of address lines and bank lines must also increase, requiring more I/O pads and greater area for disposition thereof.
In U.S. Pat. No. 6,176,569; Anderson, et al. describes a print head driving method. The disclosed method however is complex and still requires more address lines and bank lines.
Another driving circuit disclosed in U.S. Pat. No. 6,431,677, faces similar disadvantages.